1. Field of the Invention
The present invention relates to the technical of touch panels and, more particularly, to a self-capacitance input device with hovering touch.
2. Description of Related Art
With rapid spread of smart phones and tablet computers that enables touch input and multi finger gesture operation to be popular, the requirement of hovering gesture operations is then getting more and more important. Hovering detectors are already used in various smart phones to give an added value to the smart phones. The hovering detectors can detect approaching, leaving, position, and moving direction of an object without having to come into touch with the object. However, the hovering gesture detectors on the market mostly use optical photographic or infrared scanning modes, which are likely to encounter the problems of hand shadow, ambient light interference, and power consumption, resulting in disadvantage to the applications of a mobile device.
A projected capacitive touch control has the advantages of power saving, long lifetime, compact mechanism, and simple product design, and this is especially suitable for the applications of mobile electronic devices. The capacitance detection scheme for the projected capacitive touch panel can be divided into self-capacitance and mutual-capacitance sensing types. FIG. 1 is a typical self-capacitance sensing system, in which one conductor line is concurrently connected to the driving and sensing units 110, 120 in order to first drive the conductor line and then sense the change of a signal on the conductor line thereby determining the magnitude of self-capacitance.
Another method of driving the capacitive touch panel is to sense a magnitude change of mutual capacitance Cm so as to determine whether there is an object approaching to the touch panel. Similarly, instead of being a physical capacitance, the mutual capacitance Cm is a capacitance produced between two conductors arranged in first and second directions. FIG. 2 is a schematic diagram of a typical mutual-capacitance sensing system. As shown in FIG. 2, the drivers 210 are disposed in the first direction (Y), and the sensors 220 are disposed in the second direction (X). At the upper half of a first period T1, the drivers 210 drive the conductor lines 230 in the first direction and use the voltage Vy_1 to charge the mutual capacitance (Cm) 250, and at the lower half of the first period T1, all sensors 220 sense voltages (Vo_1, Vo_2, . . . , Vo_n) on the conductor lines 240 in the second direction so as to obtain n data. Accordingly, m×n data can be obtained after m driving periods.
However, the prior projected capacitive touch panel is provided to achieve only the multi-touch detection, while being unable to perform hovering touch. Therefore, it is desirable to provide an improved input device with hovering touch to mitigate and/or obviate the aforementioned problems.